MESSENGER-RNAS ENCODING LIPOPROTEIN-LIPASE, FATTY-ACID SYNTHASE AND HORMONE-SENSITIVE LIPASE IN THE ADIPOSE-TISSUE OF UNDERFED-REFED EWES AND COWS

The mechanisms involved in the nutritional regulation of genes encodin g lipogenic (lipoprotein lipase (LPL) and fatty acid synthase (FAS)) a nd lipolytic (hormone-sensitive lipase (HSL)) enzymes were investigate d by comparing the levels of the corresponding mRNAs in the adipose ti ssue (AT) of underfed or underfed-refed ewes and cows. Refeeding sharp ly increased LPL and FAS activities (19-25- and 6-8-fold, respectively ) and moderately increased (2-4 fold) the activities of glucose-6-phos phate dehydrogenase (G6PDH), malic enzyme (ME) and glycerol-3-phosphat e dehydrogenase (G3PDH). Northern blot analysis revealed three LPL tra nscripts and a single FAS transcript in cow and ewe AT. A single HSL m RNA was detected in cow AT and two transcripts in ewe AT. Refeeding sh arply increased LPL and FAS mRNA levels, while restriction slightly in creased (cows) or had no effect (ewes) on the HSL mRNA levels. This su ggests that nutritional factors regulate sharply the expression of LPL and FAS genes by pretranslational mechanisms, but less clearly that o f HSL gene. (C) Inra/Elsevier, Paris.